Standard Wireline Data Processing



Science operator: Texas A&M University
Hole: U1473A
Expedition: 362T
Location: SW Indian Ridge (SW Indian Ocean)
Latitude: 32° 42.3622' S
Longitude: 57° 16.688' E
Logging date: July 12, 2016
Sea floor depth (driller's): 721 m DRF
Sea floor depth (logger's): 721 m WRF
Total penetration: 1510.2 m DRF (789.2 m DSF) during Expedition 360 / Total penetration: 1529.4 m DRF (789.2 m DSF) during Expedition 362T
Total core recovered: 469.15 m (63.2 % of cored section) during Expedition 360 / 16.55 m (86 % of cored section) during Expedition 362T
Oldest sediment recovered: N/A
Lithology: Olivine gabbro






The logging data was recorded by Schlumberger in DLIS format. Data were processed at the Borehole Research Group of the Lamont-Doherty Earth Observatory in July 2016.


Logging Runs

Tool string
Top depth (m WMSF) Bottom depth (m WMSF) Pipe depth (m WMSF) Notes





Hole U1473A, previously drilled and logged during Expedition 360, was succesfully re-entered with an open ended drill pipe assembly. The hole was not flushed to ensure that the formation would not be disturbed and therefore the temperature profile would reflect the equilibrium in-situ temperature. The drill pipe was set at 796.7 mbrf (75.6 mbsf) in order to guide the logging tools into the open hole without a sub-sea riser system. No problems were encountered getting the tool string into the drill pipe. However, a bridge was encountered at about 998 mbrf (277 mbsf), which prevented reaching the bottom of the hole at 1529.4 mbrf (789.2 mbsf). An uplog was recorded from that depth. As expected, the temperature recorded at the bottom of the logged interval was a few degrees lower thatn that recorded during Expedition 360.


The depths in the table are for the processed logs (after depth matching between passes and depth shift to the sea floor). Sometimes, discrepancies may exist between the sea floor depths determined from the downhole logs and those determined by the drillers from the pipe length. Typical reasons for depth discrepancies are ship heave, wireline and pipe stretch, tides, and the difficulty of getting an accurate sea floor from a 'bottom felt' depth in soft sediment. Also, note that the drill pipe depth, given by the drillers at 75.6 mbsf, appears to be at 73 mbsf on the depth-matched and depth-shifted logs.




Depth shift to sea floor and depth match. The original logs were first matched to Pass 3 of the FMS/DSI/GPIT/EDTC/HNGS recorded during Expedition 360, which was used as the Reference run during that expedition. They were then depth-shifted to the sea floor (-721 m).


Depth matching is typically done in the following way. One log is chosen as reference (base) log (usually the total gamma ray log from the run with the greatest vertical extent and no sudden changes in cable speed), and then the features in the equivalent logs from the other runs are matched to it in turn. This matching is performed manually. The depth adjustments that were required to bring the match log in line with the base log are then applied to all the other logs from the same tool string.


Environmental corrections. The HNGS data were corrected for hole size during the recording.


High-resolution data. EDTC (gamma ray) data were sampled every 5.08 cm, in addition to the standard sampling rate of 15.24 cm.


Quality Control


The quality of the data is assessed by checking against reasonable values for the logged lithologies, by repeatability between different passes of the same tool, and by correspondence between logs affected by the same formation property (e.g. the resistivity log should show similar features to the sonic velocity log). The gamma ray data show a good correlation with the same dataset acquired during Expedition 360.


Gamma ray logs recorded through the drill pipe should be used only qualitatively, because of the attenuation of the incoming signal.

A null value of -999.25 may replace invalid log values.


Additional information about the drilling and logging operations can be found in the Operations and Downhole Measurements sections of the expedition report, Proceedings of the International Ocean Discovery Program, Expedition 362T. For further questions about the logs, if the hole is still under moratorium please contact the staff scientist of the expedition.

After the moratorium period you may direct your questions to:


Cristina Broglia

Phone: 845-365-8343

Fax: 845-365-3182

E-mail: Cristina Broglia


Tanzhuo Liu

Phone: 845-365-8630

Fax: 845-365-3182

E-mail: Tanzhuo Liu